DDX5: a versatile RNA helicase in cancer and cell fate determination-linking c-Myc and JAK2 V617F signalling to emerging therapeutics.
Key claim: DDX5 acts as a helicase-independent scaffolding co-activator required for JAK2 V617F-driven MPN transformation and forms a positive feedback loop with c-Myc, making it a promising therapeutic target via the small-molecule degrader FL118.
Abstract
Traditionally regarded as a DEAD-box RNA helicase involved in RNA metabolism, DDX5 (also known as p68) has emerged as a signal-responsive regulator that integrates RNA processing with transcriptional control, thereby influencing cell fate determination and tumourigenesis. Beyond its canonical roles in pre-mRNA splicing, ribosome biogenesis, microRNA maturation and R-loop resolution, DDX5 also functions in a helicase-independent manner as a transcriptional co-activator for diverse transcription factors and signalling pathways. Recent studies have revealed a dichotomy in which the RNA helicase activity and scaffolding/co-activator functions of DDX5 are selectively deployed in a context-dependent manner. In cancer, DDX5 enhances the transcriptional activity and transforming capacity of the proto-oncogene c-Myc and is itself transcriptionally induced by c-Myc, forming a positive feedback loop that sustains oncogenic transcriptional programs. DDX5 is also indispensable for transformation driven by the constitutively active JAK2 V617F mutant, a major driver of myeloproliferative neoplasms, where it promotes malignant signalling largely independently of its RNA helicase activity. In contrast, during adipocyte differentiation, the helicase function of DDX5 is essential for glucocorticoid receptor transcriptional programs. Importantly, recent studies have identified the small-molecule compound FL118 as a potent DDX5 degrader, providing proof of concept that targeting DDX5 protein stability represents a promising therapeutic strategy.
Why this matters
DDX5 emerges as a shared JAK2 V617F–dependent transformation node across PV, ET, and PMF, offering a common mechanistic target for the ~50–95% of these subtypes driven by JAK2V617F. Because DDX5’s role is helicase-independent and scaffolds a c-Myc feedback loop, FL118-mediated degradation represents a non-catalytic strategy distinct from mutant-selective (PRT12396) and type II (AJ1-11095) JAK2 inhibitors, potentially bypassing pan-JAK resistance and cytopenia liabilities. If validated, DDX5 would unify JAK2-driven MPN pathogenesis across subtypes at the transcriptional co-activator level.